Zeroth Law of Thermodynamics MCQ – Objective Questions with Answers
Mechanical Engineering › Thermodynamics | Free practice MCQs with detailed explanations
Last Updated: June 2026
📌 About this MCQ Set
The Zeroth Law of Thermodynamics establishes the concept of temperature and thermal equilibrium, providing the basis for temperature measurement.
These MCQs cover thermal equilibrium, the transitive property, and why it underpins thermometry.
8 questions • every answer comes with a worked explanation. Click Show Answer to check yourself.
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Zeroth Law of Thermodynamics MCQs
Q1. The Zeroth Law of Thermodynamics deals with:
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Answer: B. Thermal equilibrium and temperature
It defines thermal equilibrium and gives meaning to temperature.
Q2. If body A is in thermal equilibrium with B, and B with C, then A and C are:
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Answer: B. In thermal equilibrium with each other
This transitive property is the essence of the Zeroth Law.
Q3. The Zeroth Law provides the basis for:
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Answer: B. Temperature measurement (thermometry)
It justifies using a thermometer: equilibrium with the thermometer implies equal temperature.
Q4. Two bodies are in thermal equilibrium when they have the same:
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Answer: C. Temperature
Thermal equilibrium means no net heat flow, which occurs when temperatures are equal.
Q5. The Zeroth Law is called ‘zeroth’ because:
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Answer: C. It was formalised after the First and Second Laws but is more fundamental
It was named later but is logically prior to the First and Second Laws, hence ‘zeroth’.
Q6. A thermometer works on the principle of the:
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Answer: C. Zeroth Law
A thermometer reaches thermal equilibrium with the body; the Zeroth Law guarantees equal temperature.
Q7. When two systems are in thermal equilibrium, the net heat transfer between them is:
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Answer: B. Zero
At thermal equilibrium there is no temperature difference, so net heat transfer is zero.
Q8. The property that is equal for all bodies in thermal equilibrium is:
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Answer: B. Temperature
Temperature is the property that is common and equal at thermal equilibrium.
Frequently Asked Questions
What is the Zeroth Law of Thermodynamics?
If two systems are each in thermal equilibrium with a third, they are in thermal equilibrium with each other — which defines temperature.
Why is it called the Zeroth Law?
It was recognised and named after the First and Second Laws, but because it is logically more fundamental it was placed before them as the ‘zeroth’.
How does the Zeroth Law relate to thermometers?
It guarantees that a thermometer in equilibrium with a body shares its temperature, making temperature measurement meaningful.